The objective of this project is to characterize the DNA, RNA and chromosomes of dinoflagellates in order to ascertain their relationship to prokaryotes and eukaryotes. The renaturation kinetic studies will be continued on Gymnodinium sp. strain 160, a freshwater, photosynthetic dinoflagellate in order to determine whether the typical eukaryotic pattern of interspersed, repeated DNA found in the marine, nonphotosynthetic dinoflagellate C. cohnii is a general characteristic for the DNA of all dinoflagellates. DNA-RNA hybridization studies using total RNA, ribosomal RNA and poly-A containing messenger RNA (if it exists) will be initiated. The purpose of these studies is to determine what fraction of extremely large amount of dinoflagellate DNA per cell actively transcribes RNA. Molecular evolution studies using S5 rRNA two dimensional fingerprints of dinoflagellates and other primitive algae will be initiated to attempt to determine the phylogenetic position of dinoflagellates with respect to other algae, bacteria and eukaryotes. Such studies on dinoflagellates should be of special interest because of the assumed intermediate evolutionary position of dinoflagellates between prokaryotes and eukaryotes. BIBLIOGRAPHIC REFERENCES: Loeblich, III, A.R. 1975. A seawater medium for dinoflagellates and the nutrition of Cachonina niei. J. Phycol. 11:80-86. Loeblich, A.R., III. 1976. Dinoflagellates: evidence and speculation concerning their evolution. J. Protozool. 23:13-28.